Fluororubbers are known to be excellent in chemical resistance, oil resistance, and heat resistance, and also to have good compression set resistance at high temperatures. Fluororubbers are now desired to have better mechanical properties at high temperatures, such as strength at high temperature and elongation at high temperature. For example, when a cross-linked fluororubber product is used at as high temperature as more than 100° C., the product is required to have excellent mechanical properties at high temperatures as well as heat resistance, for high durability.
In terms of an increase in the compression set resistance, compositions such as one taught in Patent Document 1 have been proposed. Those compositions, however, have low elongation at room temperature, and therefore will probably have lower elongation at high temperature. The composition described in Patent Document 2 has higher elongation at high temperature, but does not have resistance to more severe use environment. The combination of a fluororubber and a thermoplastic fluoroelastomer in Patent Document 3 is an example of higher strength at high temperature, but the elongation at room temperature of this composition is also low, and therefore the elongation at high temperature will probably be even lower.    Patent Document 1: JP S60-55050 A    Patent Document 2: JP 2008-184496 A    Patent Document 3: JP H06-25500 A